A typical method of aligning an optical fiber with a laser diode involves a single base unit that has an oversized hole that accepts the laser diode on one side and a fiber optic ferrule on the other. The fiber ferrule is often affixed to the base using a method such as clamping, gluing, welding, etc. Alignment is accomplished by moving the laser diode around in the oversized hole, often with an XY scanning motion, until a suitable alignment condition has been met. The laser diode is then affixed in position using techniques such as glue, solder, laser welding, etc.
In other variations, alignment is accomplished by first affixing the laser diode in position and the fiber position is varied until a suitable alignment is obtained. Various sleeves can be used to help support the fibers and provide increased surface area to aid with the bonding/affixing step. In some applications, a bare fiber is aligned with a bare laser diode die using micro-positioning equipment, and then a drop of solder is melted with a laser and allowed to cool and harden in order to try and capture the fiber in a precise state of alignment.
Most of the conventional techniques are permanent, meaning that attempts to disassemble them can cause permanent damage to some of the components. They also are likely to require expensive, high precision positioning equipment and tooling to conduct the alignment procedure. Finally, although many of the conventional techniques can produce well-aligned assemblies, they often suffer from limited strength due to limited physical overlap of the welded or bonded components. Adhesives are commonly used to bond the components together in an aligned assembly. However, during the cure, out-gassing can damage components and many adhesives shrink when curing, potentially destroying a high precision alignment. Adhesives also have many potential durability issues. Humidity and temperature effects can cause swelling, creeping or loss of strength, resulting in joint failure or loss of alignment. The use of welding as a bonding method avoids some of the issues with adhesives, but can result in dangerously heating the components, requiring complicated and sometimes lengthy procedures to avoid causing damage. Welding is not very compatible with very high precision applications such as single mode fiber alignment because the heat of the welding process can cause enough physical deflection to destroy precise alignments. Soldering techniques used in bonding avoid some issues with adhesives but also suffer from drawbacks associated with the relatively long time it takes molten solder to cool and solidify. High precision alignments can drift or be deflected during the solder cooling process.